I have planned to buy the 55mm Fe 1.8 lens to A7, but after reading DXOmark tests I am not so sure. Nikon 50mm 1.8 G and 85mm 1.8 G get as good score numbers with d800E, but they are much cheaper. I have them both in my Nikon gear. Sony Sel 50mm 1.8 Oss score number is 23 with Sony Nex7 and with EF 55 1.8 number is 25, only two point better.

I have Sel 50mm 1.8 Oss and it works fine in crop mode and also in ff-mode, but after cropping the vignetting I get a picture corresponding some 60mm angle on view with A7.

The answer isDo I really get much better output with Zeiss FE 55mm 1.8?

I Found almost same thing when comparing Zeiss 35mm 2.8 Fe and excellent Sigma 30mm 2.8. In crop mode. Not big difference and after DXO they share same score number with Nex7.

Zeiss/Sony FE lenses are very expensive when compared with new Nikon G lenses.

You're comparing apples and oranges and then to pineapples. The FE 55/1.8 is 55mm. The SEL5018 with OSS is designed to be shot as 75mm equiv. Why are you comparing 55mm with 75mm? Also then you compare Mirrorless lenses to DSLR lenses. Why? They look the same if you're looking at them as numbers on a screen, but they are all completely differently designed.